Barrel-Type Pump with Venting Device and Associated Method

ABSTRACT

A centrifugal pump with a barrel casing and a ventilation arrangement is provided. A plug-in unit is arranged in the barrel casing. The plug-in unit has a shaft, and at least one impeller is arranged on the shaft. The impeller is enclosed by a stage casing. The stage casing separates an inner pressure space from an outer pressure space. At least one venting device is arranged in the stage casing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT International Application No. PCT/EP2015/066743, filed Jul. 22, 2015, which claims priority under 35 U.S.C. §119 from German Patent Application No. 10 2014 214 805.7, filed Jul. 29, 2014, the entire disclosures of which are herein expressly incorporated by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a centrifugal pump having a barrel casing.

A type of centrifgual pump has a plug-in unit is arranged in the barrel casing, said plug-in unit having a shaft, on which at least one impeller is arranged, which is enclosed by a stage casing separating an inner pressure space from an outer pressure space. Such designs of centrifugal pump are also referred to as barrel-type pumps, double casing pumps or can pumps. A barrel-type pump of this kind is described in DE 40 05 923 A1, for example.

These pumps are enclosed by a can-like casing. These are often multi-stage pumps for use as high- and ultrahigh-pressure pumps. Such pumps may be used, for example, as boiler feed pumps in power stations. In addition, such multistage barrel-type pumps are used in the steel industry and in the petrochemical industry, e.g. in refineries.

German patent publication no. DE 43 10 467 A1 describes a centrifugal pump of can-type design. Flow-guiding stage casings are arranged between the individual pump impellers.

German utility patent no. DE 298 19 363 U1 relates to a centrifugal pump having a barrel casing. The barrel casing has an inlet, through which a pumping medium flows. A plug-in unit is arranged in the barrel casing. The plug-in unit comprises a shaft, on which a plurality of impellers and guide vanes with the associated stage casings are arranged. The stage casings separate an inner pressure space, in which the impellers are arranged, from an outer pressure space between the stage casings and the barrel casing.

Barrel-type pumps must be subjected to a pressure test before being used. In the case of conventional barrel-type pumps, this purpose is served by designing the barrel casing, which forms the pressurized shell of the pump, for the maximum test pressure on the delivery side. The pressure test must be carried out before final assembly.

It is the object of the invention to provide a barrel-type pump in which a pressure test is possible in the assembled state. The pump should be distinguished by reliable and low-cost operation. Moreover, it should have a long service life. Furthermore, it should be possible to manufacture the barrel-type pump as inexpensively as possible and it should be distinguished by simplicity of assembly. Repeat tests in the plant should be time-saving and low-risk.

According to the invention, an opening for venting is introduced into a stage casing of the centrifugal pump. The centrifugal pump according to the invention allows priming of the pump in the fully assembled state with automatic venting of the stage casing. In contrast to conventional barrel-type pumps, in which no air can escape from an inner pressure space via the stage casing since the joint between the stage casings forms a metal seal, the pump according to the invention has a venting device.

The venting device preferably comprises at least one opening, which connects the inner pressure space to the outer pressure space. In conventional centrifugal pumps, resetting a pump for hydrostatic pressure testing, e.g. in a power station or in a refinery, takes up several working days. This considerable expenditure of time is very largely eliminated when using the barrel-type pump according to the invention since there is no need for the at least partial disassembly of the pump and the separation of the pressurized shell into a high-pressure and a low-pressure space by means of a special tool. This allows a considerable cost reduction since several barrel-type pumps are often used in parallel in power stations and in refineries and a considerable amount of work on each of these pumps is saved by means of the design according to the invention.

The pump is primed in the fully assembled state, and, by means of the venting device, air can escape from the inner pressure space via the opening in the stage casing. A barrel-type pump with automatic venting of the stage casing is thus provided.

In a particularly advantageous embodiment of the invention, the venting device comprises an element which can enable media exchange from the inner pressure space to the outer pressure space or can effect blockage of the media exchange between the inner and the outer pressure space. This element makes it possible for air to escape first of all from the inner pressure space via the venting device as the barrel-type pump is being primed. Once the barrel-type pump has been primed with the operating medium, e.g. water, this element closes the opening and thus blocks media exchange between the inner and the outer pressure space. This prevents operating medium from flowing from the outer pressure space into the inner pressure space.

This element is preferably arranged in a guide. The guide allows the element to move. By means of this movement, it is possible for the element either to enable media exchange between the inner and the outer pressure space, e.g. for venting, or to block media exchange, thus making it impossible for operating fluid to flow back from the outer pressure space into the inner pressure space after the priming of the barrel-type pump.

For this purpose, a receptacle, in which the element is arranged, can be introduced into the stage casing. The receptacle can be a bore, in which the cylinder- or disk-shaped element is positioned, for example. Here, the walls of the receptacle form the lateral guide for the element and a means of limiting movement.

The opening preferably merges into a receptacle. Thus, for example, the opening can also be embodied as a bore in the stage casing, wherein the diameter of the opening bore is smaller than the diameter of the receptacle bore in which the element is positioned. Thus, the connection introduced into the stage casing between the inner and the outer pressure space widens from a smaller opening diameter to a larger receptacle diameter, which serves both as a sealing surface and to limit the movement of the element used for sealing.

According to the invention, there is still a sufficiently large free cross section available between the walls of the receptacle and the element to allow air to escape. The air flows through the opening into the receptacle and then through the free cross section between the element and the walls of the receptacle into the outer pressure space.

The element is of larger design than the opening. This feature is a prerequisite for the element being able to close the opening in the case of backflow of the operating medium. In this embodiment of the invention, the venting device is thus equipped with a backflow safeguard. If the pressure in the outer pressure space rises above the pressure in the inner pressure space, the element is pressed onto the opening and media exchange is prevented.

In this arrangement, the cylinder- or disk-shaped element is pressed onto the bottom of the receptacle and closes the opening introduced into the bottom of the receptacle by means of a suitable sealing surface design, e.g. an annular raised portion which faces the stage casing and is formed integrally with the element.

The venting device preferably has a stop for the element. This can be arranged on the walls of the receptacle, for example. This can be a projection which protrudes into the receptacle and thus prevents the element from being washed out of the receptacle or jammed. In this case, the stop preferably protrudes into the receptacle only at certain points, and therefore there is always a free cross section remaining for air to escape.

The venting device is preferably arranged in an upper region of the stage casing, wherein, in particular, a 12 o'clock position is suitable since the air collects at the highest point.

Another object of the invention is to make available a method for carrying out pressure testing of a barrel-type pump.

According to the invention, the barrel-type pump is first of all fully assembled. The centrifugal pump is then primed with operating medium. In the method according to the invention, air can escape from the stage casings in the fully assembled state.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an axial section through a barrel-type pump in accordance with the present invention,

FIG. 2 shows a schematic illustration of the venting device in accordance with the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a centrifugal pump having a barrel casing 1. A plug-in unit 2 is arranged in the barrel casing 1. The plug-in unit 2 comprises a shaft 3, on which a plurality of impellers 4 is arranged in series. In the illustrative embodiment, the impellers 4 are radial impellers.

Each impeller 4 is enclosed by a stage casing 5. Adjacent stage casings 5 adjoin one another. The joint between the stage casings 5 forms a metal seal in the illustrative embodiment.

Formed integrally on the barrel casing 1 is an intake connection 6, through which the operating medium enters the centrifugal pump. The operating medium leaves the centrifugal pump via a discharge connection 7.

According to the invention, a venting device 8 is arranged in an upper region in the pressure casings 5, in each case in a 12 o′clock position. The barrel-type pump according to the invention can thus be subjected to a pressure test in the fully assembled state. This is only made possible by the integration of the venting devices 8. The venting devices 8 ensure that the barrel-type pumps that are already fully installed in the plant can be primed and that, in the process, air can escape via the venting devices 8.

FIG. 2 shows a schematic illustration of a venting device 8. The venting device 8 is integrated into each stage casing 5. The stage casing 5 separates an inner pressure space 9 from an outer pressure space 10. The inner pressure space 9 is arranged around the impellers 4. The outer pressure space 10 is situated between the stage casing 5 and the barrel casing 1 and is connected in terms of pressure to the interior of the discharge connection 7.

According to the invention, the venting device 8 comprises an opening 11, which is introduced as a bore into the stage casing 5. The venting device 8 furthermore comprises a receptacle 12. The receptacle 12 is a depression which, in the illustrative embodiment, is introduced as a circular recess in the form of a bore into the outer circumferential surface of the stage casing 5. It forms a region of the opening 11 of enlarged inside diameter. Arranged in the receptacle 12 is an element 13. In the illustrative embodiment, the element 13 is a disk-type element, which is of cylindrical design. The diameter of the element 13 is smaller than the diameter of the receptacle 12, and therefore the element 13 is arranged in the receptacle 12 in such a way as to be movable in the radial direction.

In the variant illustrated in FIG. 2, the venting device 8 comprises a stop 14, which prevents the element 13 from being carried out of the receptacle 12. The stop 14 can comprise projections which protrude into the receptacle 12 or a snap ring inserted into an annular groove provided in the receptacle 12.

If the barrel-type pump is primed with operating medium for pressure testing, the element 13 is pushed upward or outward in a radial direction and opens a free cross section for the escape of the air. The stop 14 acts as a safety element and prevents the element 13 from being carried out of the receptacle 12, e.g. by vibration during operation or by the air flow during venting. During the priming process, the rising operating medium in the inner pressure space 9 raises the element 13 by means of the hydrostatic water column until all the air has escaped. The fully vented system is then put into operation. During operation, a higher operating pressure is established in the outer pressure space 10 than in the inner pressure space 9. Owing to this pressure difference, the element is pressed against the bottom of the receptacle 12 in the stage casing 5. The element 13 is embodied as a sealing element and prevents operating medium from flowing back from the outer pressure space 10 into the inner pressure space 9. For this purpose, the contact surfaces between the bottom of the receptacle 12 and the element 13 are embodied in such a way that reliable sealing is ensured.

The venting device according to the invention manages completely without spring elements. By dispensing with spring elements, the venting device according to the invention proves to be free from wear and requires little maintenance. It is distinguished by reliable operation and a long service life. Moreover, no further energy source is required apart from the operating medium. Thus, the venting device according to the invention is independent of external energy sources and does not additionally increase operating costs.

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. 

1-14. (canceled)
 15. A centrifugal pump, comprising: a barrel casing; at least one stage casing located within the barrel casing between an inner pressure space radially inside the at least one stage casing and an outer pressure space between the at least one stage casing and the barrel casing; and at least one venting device arranged in the at least one stage casing arranged to control flow of a media between the inner pressure space and the outer pressure space.
 16. The centrifugal pump as claimed in claim 15, wherein each of the at least one venting devices is arranged in a corresponding opening in the at least one stage casing, each opening being arranged to connect the inner pressure space to the outer pressure space.
 17. The centrifugal pump as claimed in claim 16, wherein each of the at least one venting devices includes a corresponding flow control element configured to cooperate with the corresponding opening to enable or block flow of the media between the inner pressure space and the outer pressure space.
 18. The centrifugal pump as claimed in claim 17, wherein the flow control element is arranged in a guide.
 19. The centrifugal pump as claimed in claim 18, wherein the guide is a receptacle in the at least one stage casing configured to receive the flow control element.
 20. The centrifugal pump as claimed in claim 19, wherein the opening located on a radially inward side of the receptacle.
 21. The centrifugal pump as claimed in claim 20, wherein a free cross section for media exchange is present between a wall of the receptacle and the flow control element.
 22. The centrifugal pump as claimed in claim 21, wherein the receptacle is a receptacle bore in the at least one stage casing.
 23. The centrifugal pump as claimed in claim 22, wherein the opening is an opening bore into the at least one stage casing.
 24. The centrifugal pump as claimed in claim 23, wherein a surface of the flow control element arranged is larger a diameter of the opening, such that when the flow control element is in a flow blocking position media flow through the opening is blocked.
 25. The centrifugal pump as claimed in claim 24, wherein the flow control element is a disk.
 26. The centrifugal pump as claimed in claim 24, wherein the venting device includes a stop arranged to prevent movement of the flow control element out of the receptacle bore.
 27. The centrifugal pump as claimed in claim 15, wherein the venting device is arranged in an upper region of the at least one stage casing. preferably in a 12 o'clock position.
 28. The centrifugal pump as claimed in claim 27, wherein the venting device is located at a highest location at which gas accumulates.
 29. A method for performing a pressure test in a centrifugal pump as claimed in claim 1 at a location at which the pump is installed, comprising the steps of: priming the centrifugal pump with the media; maintaining the flow control element in a flow-enabled position while gas is purged from the inner pressure space to the outer pressure space; and maintaining the flow control element in a flow-blocked position after the gas is purged from the inner pressure space to the outer pressure space.
 30. The method for performing a pressure test as claimed in claim 29, wherein after the media in the inner pressure space enters the at least one venting device, the flow control element shifts between the flow-enabled position and the flow-blocked position. 